Buoyed up

Q.Swimming instructors will tell you the world divides into two types: "sinkers" and "floaters." If you're a sinker, is there anything you can do about it? ­E. Williams

A. Try heading for the salty ocean or, if that doesn't do it, the super salty Great Salt Lake in Utah or Dead Sea between Israel and Jordan, says physicist Peter J. Brancazio in Sport Science. Many people unable to float in fresh water find they can in ocean water, whose density is about 2.5 percent higher.

The reason for the range of floating abilities is that the human body has a specific gravity close to that of fresh water (1.0 specific gravity), so extra body fat (0.8) helps buoy a person, muscle (1.0) doesn't help, and bone is a real drag (1.5-2.0). Because of this, women with their higher proportion of body fat generally float more easily than men.

In the buoyant Great Salt Lake or Dead Sea, you may back-float so high you can hold head and hands above the water and read a book– as on a water hammock.

"Anyone can float in these waters without difficulty– but accidentally swallowing a mouthful of the stuff can be a truly awful experience."

Q.You've heard about the tongue's four distinct taste regions– bitter, sour, salty and sweet. How were these first mapped? ­J. Child

A. Mistakenly! A misinterpretation of research in the late 1800s led to the famous "taste map," a common feature of textbooks since the early 1900s, report anatomist David Smith and physiologist Robert Margolskee in Scientific American. But it should have left a bad taste in everyone's mouth because it is all wrong. In reality, all qualities of taste can be elicited in all tongue regions. Taste experts now know the map was a mistake, but with its long history, "It has been almost impossible to purge from the literature."

A. Plenty, says Michigan State University veterinary medicine student Brian Dawson. A one-year-old dog has reached sexual maturity, but even a precocious seven-year-old human has a way to go. At the other end of the scale, the world's oldest dog at 29 would be 203!

So the formula breaks down, especially at the extremes. "Since dogs' life spans are usually limited to 15-20 years, it should be enough to say that a two-year-old dog is young, a nine-year-old is middle-aged, and a 14-year-old is old."

If you must apply a formula, try this: Count dog year No. one as 15 human years, year No. two as 10 more, every year after that as an additional three. This way, a 10-year-old dog corresponds more realistically with a 49-year-old human, not a 70-year-old.

Q."Have a NICE day." Nice of you to say so nowadays, but what if you'd said it to someone in England c. 1200? ­N. Chomsky

A. "Nice" has a rich history, borrowed from Latin as NESCIUS, or "not knowing," says University of California-Berkeley linguist John McWhorter. As such, in the 1200s it meant "foolish" or "ignorant." Later the meaning drifted (via unclear logic) to suggest "extravagant" (Chaucer), then "precise" and "discriminating" (a "nice" distinction), soon also "dainty" (in an aunty, antimacassar kind of way).

And it seems to be from here that the current meaning of "pleasant" comes, which has only been dominant for a few centuries. "Thus 'Have a nice day' meant different things in different periods, and 800 years ago would have been rather like telling someone to dumb down for a day."